Freezing of dendritic cells with trehalose as an additive in the conventional freezing medium results in improved recovery after cryopreservation

Co-delivery of dendritic cell vaccine and anti-PD-1 antibody with cryomicroneedles for combinational immunotherapy

Combinational immunotherapy of dendritic cell (DC) vaccines and anti-programmed cell death protein 1 antibodies (aPD1) has been regarded as a promising strategy for cancer treatment because it not only induces tumor-specific T cell immune responses, but also prevents failure of T cell functions by the immune suppressive milieu of tumors. Microneedles have emerged as an innovative platform for efficient transdermal immunotherapies. However, co-delivery of DC vaccines and aPD1 via microneedles has not been studied since conventional microneedle platforms are unsuitable for fragile therapeutics like living cells and antibodies. This study employs our newly invented cryomicroneedles (cryoMNs) to co-deliver DC vaccines and aPD1 for the combinational immunotherapy. CryoMNs are fabricated by stepwise cryogenic micromoulding of cryogenic medium with pre-suspended DCs and aPD1, which are further integrated with a homemade handle for convenient application. The viability of DCs in cryoMNs remains above 85%. CryoMNs are mechanically strong enough to insert into porcine and mouse skin, successfully releasing DCs and aPD1 inside skin tissue after melting. Co-delivery of ovalbumin (OVA)-pulsed DCs (OVA-DCs) and aPD1 via cryoMNs induced higher antigen-specific cellular immune responses compared with the mono-delivery of OVA-DCs or aPD1. Finally, administration with cryoMNs co-encapsulated with OVA-DCs and aPD1 increases the infiltration of effector T cells in the tumor, resulting in stronger anti-tumor therapeutic efficacy in both prophylactic and therapeutic melanoma models compared with administration with cryoMNs loaded with OVA-DCs or aPD1. This study demonstrates the great potential of cryoMNs as a co-delivery system of therapeutic cells and biomacromolecules for combinational therapies.

Manufacturing and validation of Good Manufacturing Practice-compliant regulatory dendritic cells for infusion into organ transplant recipients

BACKGROUND AIMS

Regulatory (or "tolerogenic") dendritic cells (DCregs) are a highly promising, innovative cell therapy for the induction or restoration of antigen-specific tolerance in immune-mediated inflammatory disorders. These conditions include organ allograft rejection, graft-versus-host disease following bone marrow transplantation and various autoimmune disorders. DCregs generated for adoptive transfer have potential to reduce patients' dependence on non-specific immunosuppressive drugs that can induce serious side effects and enhance the risk of infection and certain types of cancer. Here, our aim was to provide a detailed account of our experience manufacturing and validating comparatively large numbers of Good Manufacturing Practice-grade DCregs for systemic (intravenous) infusion into 28 organ (liver) transplant recipients and to discuss factors that influence the satisfaction of release criteria and attainment of target cell numbers.

RESULTS

DCregs were generated in granulocyte-macrophage colony stimulating factor and interleukin (IL)-4 from elutriated monocyte fractions isolated from non-mobilized leukapheresis products of consenting healthy adult prospective liver transplant donors. Vitamin D3 was added on day 0 and 4 and IL-10 on day 4 during the 7-day culture period. Release and post-release criteria included cell viability, purity, phenotype, sterility and functional assessment. The overall conversion rate of monocytes to DCregs was 28 ± 8.2%, with 94 ± 5.1% product viability. The mean cell surface T-cell co-inhibitory to co-stimulatory molecule (programmed death ligand-1:CD86) mean fluorescence intensity ratio was 3.9 ± 2.2, and the mean ratio of anti-inflammatory:pro-inflammatory cytokine product (IL-10:IL-12p70) secreted upon CD40 ligation was 60 ± 63 (median = 40). The mean total number of DCregs generated from a single leukapheresis product (n = 25 donors) and from two leukapheresis products (n = 3 donors) was 489 ± 223 × 10⁶ (n = 28). The mean total number of DCregs infused was 5.9 ± 2.8 × 10⁶ per kg body weight. DCreg numbers within a target cell range of 2.5-10 × 10⁶/kg were achieved for 25 of 27 (92.6%) of products generated.

CONCLUSIONS

High-purity DCregs meeting a range of quality criteria were readily generated from circulating blood monocytes under Good Manufacturing Practice conditions to meet target cell numbers for infusion into prospective organ transplant recipients.

Trehalose in Biomedical Cryopreservation-Properties, Mechanisms, Delivery Methods, Applications, Benefits, and Problems

Cells and tissues are the foundation of translational medicine. At present, one of the main technological obstacles is their preservation for long-term usage while maintaining adequate viability and function. Optimized storage techniques must be developed to make them safer to use in the clinic. Cryopreservation is the most common long-term preservation method to maintain the vitality and function of cells and tissues. But, the formation of ice crystals in cells and tissues is considered to be the main mechanism that could harm cells and tissues during freezing and thawing. To reduce the formation of ice crystals, cryoprotective agents (CPAs) must be added to the cells and tissues to achieve the cryoprotective effect. However, conventional cryopreservation of cells and tissues often needs to use toxic organic solvents as CPAs. As a result, cryopreserved cells and tissues may need to go through a time-consuming washing process to remove CPAs for further applications in translational medicine, and multiple valuable cells are potentially lost or killed. Currently, trehalose has been researched as a nontoxic CPA due to its cryoprotective ability and stability during cryopreservation. Nevertheless, trehalose is a nonpermeable CPA, and the lack of an effective intracellular trehalose delivery method has become the main obstacle to its use in cryopreservation. This article illustrated the properties, mechanisms, delivery methods, and applications of trehalose, summarized the benefits and limits of trehalose, and summed up the findings and research direction of trehalose in biomedical cryopreservation.

Exosomes based advancements for application in medical aesthetics

Beauty is an eternal pursuit of all people. Wound repair, anti-aging, inhibiting hyperpigmentation and hair loss are the main demands for medical aesthetics. At present, the repair and remodeling of human body shape and function in medical aesthetics are often achieved by injection of antioxidants, hyaluronic acid and botulinum toxin, stem cell therapy. However, there are some challenges, such as difficulty controlling the injection dose, abnormal local contour, increased foreign body sensation, and the risk of tumor occurrence and deformity induced by stem cell therapy. Exosomes are tiny vesicles secreted by cells, which are rich in proteins, nucleic acids and other bioactive molecules. They have the characteristics of low immunogenicity and strong tissue penetration, making them ideal for applications in medical aesthetics. However, their low yield, strong heterogeneity, and long-term preservation still hinder their application in medical aesthetics. In this review, we summarize the mechanism of action, administration methods, engineered production and preservation technologies for exosomes in medical aesthetics in recent years to further promote their research and industrialization in the field of medical aesthetics.

Cryomicroneedles for transdermal cell delivery

Cell therapies for the treatment of skin disorders could benefit from simple, safe and efficient technology for the transdermal delivery of therapeutic cells. Conventional cell delivery by hypodermic-needle injection is associated with poor patient compliance, requires trained personnel, generates waste and has non-negligible risks of injury and infection. Here, we report the design and proof-of-concept application of cryogenic microneedle patches for the transdermal delivery of living cells. The microneedles are fabricated by stepwise cryogenic micromoulding of cryogenic medium with pre-suspended cells, and can be easily inserted into porcine skin and dissolve after deployment of the cells. In mice, cells delivered by the cryomicroneedles retained their viability and proliferative capability. In mice with subcutaneous melanoma tumours, the delivery of ovalbumin-pulsed dendritic cells via the cryomicroneedles elicited higher antigen-specific immune responses and led to slower tumour growth than intravenous and subcutaneous injections of the cells. Biocompatible cryomicroneedles may facilitate minimally invasive cell delivery for a range of cell therapies.

Cryopreservation of mesenchymal stromal cell-derived extracellular vesicles using trehalose maintains their ability to expand hematopoietic stem cells in vitro

The multitude of clinical trials using mesenchymal stromal cells (MSCs) has underscored their significance as a promising cell source for regenerative therapies. Most studies have however shown that MSCs get entrapped into the microvasculature of lungs, liver and spleen. In addition to intercellular communication, MSCs exert their effects in a paracrine manner by secretion of extracellular vesicles (EVs). The therapeutic effects of MSC-derived EVs have been examined in several diseases such as hepatic failure, liver injury, hematopoiesis etc. Therefore, optimization of cryopreservation strategies for the long-term storage of functional EVs could help in the development of off-the-shelf biologics. The aim of this study was to develop an optimal cryopreservation strategy for the efficient storage of both types of EVs - Microvesicles (MVs) and exosomes, independently, and to further examine the effect of the cryopreserved EVs on the ex vivo expansion of HSCs. MVs and exosomes were separately cryopreserved at different temperatures using PBS or PBS supplemented with trehalose (pTRE), and these cryopreserved EVs were then assessed for their functionality after revival. We found that addition of trehalose during cryopreservation helped in maintaining the morphology and functionality of the EVs, as assessed by their HSC-supportive potential, ability to expand phenotypically defined HSCs and ability to maintain the chemotactic migration potential of the HSCs co-cultured with them. This strategy could prove to be beneficial for facilitating the use of EVs as cell-free ready-to-use biologics for the ex vivo expansion of HSCs and in regenerative medicine.

Advanced Biotechnology for Cell Cryopreservation

Cell cryopreservation has evolved as an important technology required for supporting various cell-based applications, such as stem cell therapy, tissue engineering, and assisted reproduction. Recent times have witnessed an increase in the clinical demand of these applications, requiring urgent improvements in cell cryopreservation. However, cryopreservation technology suffers from the issues of low cryopreservation efficiency and cryoprotectant (CPA) toxicity. Application of advanced biotechnology tools can significantly improve post-thaw cell survival and reduce or even eliminate the use of organic solvent CPAs, thus promoting the development of cryopreservation. Herein, based on the different cryopreservation mechanisms available, we provide an overview of the applications and achievements of various biotechnology tools used in cell cryopreservation, including trehalose delivery, hydrogel-based cell encapsulation technique, droplet-based cell printing, and nanowarming, and also discuss the associated challenges and perspectives for future development.

The roles of reactive oxygen species and antioxidants in cryopreservation

Cryopreservation has facilitated advancement of biological research by allowing the storage of cells over prolonged periods of time. While cryopreservation at extremely low temperatures would render cells metabolically inactive, cells suffer insults during the freezing and thawing process. Among such insults, the generation of supra-physiological levels of reactive oxygen species (ROS) could impair cellular functions and survival. Antioxidants are potential additives that were reported to partially or completely reverse freeze-thaw stress-associated impairments. This review aims to discuss the potential sources of cryopreservation-induced ROS and the effectiveness of antioxidant administration when used individually or in combination.